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1.
The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds. 相似文献
2.
Active and passive cation transport and L antigen hertogeneity in low potassium sheep red cells 下载免费PDF全文
Several lines of experimental evidence are presented suggesting that the L antigens in low potassium (LK) sheep red cells are associated with separate Na(+)K(+) pump flux is distinct from the action of anti-L(l) on K(+) leak flux, implying that K(+) leak transport sites may not be converted into active pumps by the L antiserum. Treatment of LK red cells with trypsin completely abolished both the stimulation of K(+) pump flux and the enhancement of the rate of ouabain binding brought about by anti- L. That this effect is due to a total destruction of the L(p) determinant associated with the LK pump was evident from the complete failure of anti-L(p) to bind to trypsinized LK red cells. The L(p) antigen can be effectively protected against the trypsin attack by prior incubation with anti-L, indicating that the sites for antibody binding and trypsin action may be closely adjacent at the structural level. Trypsin treatment, however, did not interfere with anti-L(l) reducing ouabain insensitive K(+) leak influx, nor did it prevent binding of anti-L(ly), the hemolytically active L antibody which is probably identical with anti-L(l). The functional independence of the L(p) and L(l) sites was documented by the observation that anti-L(l) still reduced K(+) leak influx in LK cells with experimentally induced high potassium concentrations, at which K(+) pump flux is fully suppressed, whether or not anti-L(p) was binding to the L(p) antigen associated with the LK pump. 相似文献
3.
M J Crumpton J J Marchalonis D Haustein J L Atwell A W Harris 《The Australian journal of experimental biology and medical science》1976,54(4):303-316
Two established techniques for analysis of plasma membranes, namely, lactoperoxidase catalyzed surface radioiodination of intact cells and bulk membrane isolation following disruption of cells by shear forces, were applied in studies of membrane proteins of continuously cultured cells of the monoclonal T lymphoma line WEHI-22. It was found that macromolecular 125I-iodide incorporated into plasma membrane proteins of intact cells was at least as good a marker for the plasma as was the commonly used enzyme 5'-nucleotidase. T lymphoma plasma membrane proteins were complex when analysed by polyacrylamide gel electrophoresis in sodium dodecylsulphate-containing buffers and more than thirty distinct components were resolved. More than fifteen of the components observed on a mass basis were also labelled with 125I-iodide. Certain bands, however, exhibited a degree of label disproportionate to their staining properties with Coomassie Blue. This was interpreted in terms of their accessibility to the solvent in the intact cells. 相似文献
4.
5.
The position of localized soil compaction determines root and subsequent shoot growth responses 总被引:4,自引:0,他引:4
Plants growing in soils typically experience a mixture of loose and compact soil. The hypothesis that the proportion of a root system exposed to compact soil and/or the timing at which this exposure occurs determines shoot growth responses was tested. Broccoli (Brassica oleracea var. italica cv. Greenbelt) seedlings were grown in pot experiments with compact, loose and localized soil compaction created by either horizontal (compact subsoils 75 or 150 mm below loose topsoil) or vertical (adjacent compact and loose columns of soil) configurations of loose (1.2 Mg m(-3)) and compact (1.8 Mg m(-3)) soil. Entirely compact soil reduced leaf area by up to 54%, relative to loose soil. When compaction was localized, only the vertical columns of compact and loose soil reduced leaf area (by 30%). Neither the proportion of roots in compact soil nor the timing of exposure could explain the differing shoot growth responses to localized soil compaction. Instead, the strong relationship between total root length and leaf area (r(2)=0.92) indicated that localized soil compaction reduced shoot growth only when it suppressed total root length. This occurred when isolated root axes of the same plant were exposed to vertical columns of compact and loose soil. When a single root axis grew through loose soil into either a shallow or deep compact subsoil, compensatory root growth in the loose soil maintained total root length and thus shoot growth was unaffected. These contrasting root systems responses to localized soil compaction may explain the variable shoot growth responses observed under heterogeneous conditions. 相似文献
6.
Industrial microbiology of solar salt production 总被引:3,自引:0,他引:3
Javor BJ 《Journal of industrial microbiology & biotechnology》2002,28(1):42-47
Solar salterns can be modeled as giant outdoor chemostats, much like a series of dams on a slow-moving river. Microorganisms
and their products play an essential, but sometimes uncharacterized, role in salt production in these ponds, from seawater
salinity up through NaCl saturation. They may physically affect the evaporation process and their by-products may chemically
modify or bind with dissolved ions. Many solar salt facilities engage microbiologists to establish monitoring programs for
analyses of nutrients, standing crop and associated biological variables in the ponds. Other solar salt companies engage microbiologists
only when there are “crises” in the ponds that interfere with salt production. Journal of Industrial Microbiology & Biotechnology (2002) 28, 42–47 DOI: 10.1038/sj/jim/7000173
Received 20 May 2001/ Accepted in revised form 13 June 2001 相似文献
7.
ANDREAS LUEK GEORGE E. MORGAN BJÖRN WISSEL JOHN M. GUNN CHARLES W. RAMCHARAN 《Freshwater Biology》2010,55(8):1616-1627
1. Yellow perch (Perca flavescens) are often the only surviving fish species in acidified lakes. We studied four lakes along a gradient of recovery from acidification and that had different food web complexities. All had abundant yellow perch, two had low piscivore abundance, one had a well‐established piscivore population and one was manipulated by introducing piscivorous smallmouth bass (Micropterus dolomieu). We hypothesised that there would be strong effects on perch abundance, behaviour and diet induced by the presence of piscivores. 2. In the manipulated lake, the bass reduced yellow perch abundance by 75% over a 2‐year period. Concomitantly, perch use of the pelagic habitat fell from 48 to 40%. 3. In contrast to findings from less disturbed systems, yellow perch in the littoral zone of the manipulated lake did not strongly shift from zooplankton to benthic food sources after the arrival of piscivores. Diet analysis using stable carbon isotopes revealed a strong continued reliance on zooplankton in all lakes, independent of the degree of piscivory. The failure to switch to benthos in the refuge area of the littoral zone is most likely related to the depauperate benthos communities in these formerly acidified lakes. 4. Yellow perch in lakes recovering from acidification face a considerable ecological challenge as the necessary switch to benthic diet is hindered by a low abundance of benthos. The arrival of piscivores in these recovering lakes imposes further restrictions on perch access to food items. We infer that future recovery of perch populations (and higher trophic levels) will have to be preceded by the re‐establishment of diverse benthic macroinvertebrate communities in these lakes. 相似文献
8.
Ante Jerkovic Alison M. Kriegel John R. Bradner Brian J. Atwell Thomas H. Roberts Robert D. Willows 《Plant physiology》2010,152(3):1459-1470
Bran from bread wheat (Triticum aestivum ‘Babbler’) grain is composed of many outer layers of dead maternal tissues that overlie living aleurone cells. The dead cell layers function as a barrier resistant to degradation, whereas the aleurone layer is involved in mobilizing organic substrates in the endosperm during germination. We microdissected three defined bran fractions, outer layers (epidermis and hypodermis), intermediate fraction (cross cells, tube cells, testa, and nucellar tissue), and inner layer (aleurone cells), and used proteomics to identify their individual protein complements. All proteins of the outer layers were enzymes, whose function is to provide direct protection against pathogens or improve tissue strength. The more complex proteome of the intermediate layers suggests a greater diversity of function, including the inhibition of enzymes secreted by pathogens. The inner layer contains proteins involved in metabolism, as would be expected from live aleurone cells, but this layer also includes defense enzymes and inhibitors as well as 7S globulin (specific to this layer). Using immunofluorescence microscopy, oxalate oxidase was localized predominantly to the outer layers, xylanase inhibitor protein I to the xylan-rich nucellar layer of the intermediate fraction and pathogenesis-related protein 4 mainly to the aleurone. Activities of the water-extractable enzymes oxalate oxidase, peroxidase, and polyphenol oxidase were highest in the outer layers, whereas chitinase activity was found only in assays of whole grains. We conclude that the differential protein complements of each bran layer in wheat provide distinct lines of defense in protecting the embryo and nutrient-rich endosperm.Wheat grain (Triticum aestivum) is a major cereal crop and staple food in many parts of the world. The endosperm is the main nutritional component and is extracted in milling to produce base ingredients such as flour and semolina. Crop yield and quality may be compromised by both environmental and biological stresses. Wheat varieties are known to vary in their resistance to such stresses, probably due to individual differences in defense protein levels (Demeke and Morris, 2002; Bonnin et al., 2005; Yarullina et al., 2005). Cereal grain contains many defense proteins that have been categorized according to their mode of action and structural similarities. A major class of these is the pathogenesis-related (PR) proteins, which include PR-1, PR-2 (β -1,3-glucanases), PR-3 (chitinases), PR-4 (wheatwin1), and PR-5 (thaumatin-like proteins; Selitrennikoff, 2001; Desmond et al., 2006). Other known defense proteins are xylanase inhibitor proteins (XIPs) and α -amylase inhibitor proteins (Mundy et al., 1984; Payan et al., 2003). All of these defense proteins have both general and specific roles that contribute to plant survival, although little is known of their location within the various grain tissues, particularly the multiple layers that constitute bran.Proteomic analysis of wheat grain has previously been applied to identify proteins in the germ and endosperm (Skylas et al., 2000; Wong et al., 2004; Mak et al., 2006), but analysis of bran and bran tissue fractions has not been reported. Collection of sufficiently pure bran tissue fractions has limited progress, mainly due to the strong bonds between the various bran tissue layers and endosperm in dry grain. Thus, a method to obtain bran layers free from contaminants, such as adjacent tissue and endosperm, is required to provide a sample suitable for proteomic analysis. Soaking whole grain in water causes the endosperm to soften, allowing it to be easily removed and washed from the bran; the bran becomes malleable enough to dissect. While this approach might not identify the proteome of dry grain fractions, it is the best available representation of the three distinct tissue fractions in grains, namely the outer layer (epidermis and hypodermis), intermediate layer (cross cells, tube cells, testa, and nucellar tissue), and inner layer (aleurone cells; Antoine et al., 2003, 2004). Using this method, water-soluble proteins that diffuse from the grain can be collected and identified.In this study we aimed (1) to dissect bran into the three separate tissue fractions described above and to identify the protein complement of each fraction using proteomics, (2) to confirm the location of three major defense proteins identified (one from each microfraction) using immunolocalization, and (3) to identify water-soluble proteins and assay any defense-related proteins for enzymatic activity. 相似文献
9.
JON E. SWENSON BJØRN DAHLE HELENA BUSK OLE OPSETH THOMAS JOHANSEN ARNE SÖDERBERG KJELL WALLIN GORAN CEDERLUND 《The Journal of wildlife management》2007,71(6):1993-1997
Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km2 and 920/1,000 km2, respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%. 相似文献
10.